Accumulated Other Comprehensive Income - Components of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss)
Total other comprehensive income (loss), before tax	$ 25,217	$ (17,557)	$ 116,113	$ (61,024)
Total other comprehensive income (loss), tax effect	(6,323)	5,109	(26,747)	14,282
Total other comprehensive income (loss), net of tax	18,894	(12,448)	89,366	(46,742)
Debt securities available for sale and interest-only strips
Net unrealized gains (losses) arising during the period, before tax	24,236	(18,086)	114,263	(62,521)
Net unrealized gains (losses) arising during the period, tax effect	(5,606)	4,516	(27,519)	15,688
Net unrealized gains (losses) arising during the period, net of tax	18,630	(13,570)	86,744	(46,833)
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), before tax	791	179	632	1,031
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), tax effect	(191)	(43)	(153)	(257)
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), net of tax	600	136	479	774
Net unrealized gains (losses) on debt securities available for sale and interest-only strips, before taxes	25,027	(17,907)	114,895	(61,490)
Net unrealized gains (losses) on debt securities available for sale and interest-only strips, tax effect	(5,797)	4,473	(27,672)	15,431
Net unrealized gains (losses) on debt securities available for sale and interest-only strips, net of tax	19,230	(13,434)	87,223	(46,059)
Net investment hedges
Net unrealized gains (losses) on net investment hedges, before tax	2,170	2,537	(3,761)	4,637
Net unrealized gains (losses) on net investment hedges, tax effect	(529)	(633)	915	(1,158)
Net unrealized gains (losses) on net investment hedges, net of tax	1,641	(1,904)	(2,846)	3,479
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax [Abstract]
Foreign currency translation adjustment, before tax	(1,968)	2,899	5,014	(4,136)
Foreign currency translation adjustment, tax effect	0	0	0	0
Foreign currency translation adjustment, net of tax	(1,968)	2,899	5,014	(4,136)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax [Abstract]
Reclassification of amortization of prior service cost to Other non-interest expense, before tax	(12)	(12)	(35)	(35)
Reclassification of amortization of prior service cost to Other non-interest expense, tax effect	3	3	10	9
Reclassification of amortization of prior service cost to Other non-interest expense, net of tax	(9)	(9)	(25)	(26)
Total interest income
Debt securities available for sale and interest-only strips
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), before tax	844	263	2,495	810
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), tax effect	(205)	(65)	(607)	(202)
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), net of tax	639	198	1,888	608
Gains (losses) on debt securities, net
Debt securities available for sale and interest-only strips
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), before tax	0	0	(1,513)	0
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), tax effect	0	0	368	0
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), net of tax	0	0	(1,145)	0
Other noninterest expense
Debt securities available for sale and interest-only strips
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), before tax	(53)	(84)	(350)	221
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), tax effect	14	22	86	(55)
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), net of tax	$ (39)	$ (62)	$ (264)	$ 166